SEOUL, South Korea (AP) — The Koreas’ first high-level talks in years were scrapped a day before they were to begin Wednesday because the sides didn’t agree on the delegation leaders, South Korea said. The cancellation deflated tentative hopes that the rivals would improve ties following years of rising hostility.

North Korea said it wasn’t sending its officials to Seoul for the two-day meeting because the South had changed the head of its delegation, Kim Hyung-suk, a spokesman for Seoul’s Unification Ministry, told reporters in a briefing Tuesday. The ministry is in charge of North Korea matters.

The hope was that talks on reviving two high-profile economic cooperation projects would start to mend a relationship marred earlier this year by North Korean threats of nuclear war and South Korean vows of counterstrikes. But the collapse over what’s essentially a protocol matter is testament to the difficulty the countries have in finding common ground.

South Korea had originally wanted a minister-level meeting between the top officials responsible for inter-Korean affairs, but Pyongyang wouldn’t commit to that. The last minister-level meeting between the Koreas occurred in 2007.

When Seoul told Pyongyang on Tuesday that it was sending a lower-level official than it had initially proposed in preparatory talks, North Korea said it would consider that a “provocation,” Kim said.

The cancellation arises partly from misunderstandings that the sides have about who equals whom in power between their different political systems, Koh Yu-hwan, a North Korea scholar at Seoul’s Dongguk University, said.

“The two sides are offended by each other now. The relations may again undergo a cooling-off period before negotiations for further talks resume,” he said.

North Korea did not issue its own statement about the canceled talks. North Korea did not answer a call from South Korea on Wednesday morning through a Red Cross line that Pyongyang restored last week to communicate before the scrapped talks.

The talks were set up in a painstaking 17-hour negotiating session Sunday, but the rivals had set aside the issue of who would lead North Korea’s delegation. Kim said North Korea offered Tuesday to send a senior official of the Committee for the Peaceful Reunification of Korea as chief delegate, and Seoul said it would send its vice unification minister as chief delegate.

South Korea had previously proposed sending its unification minister. After it announced the vice minister would go instead, North Korea said it wouldn’t send anyone and that “all responsibility is entirely on South Korea,” Kim said. He added that Seoul is still open to talks if North Korea reconsiders.

The main goal of the planned talks had been to see if the Koreas could restore economic projects that were born in the “sunshine era,” a 10-year period ending in 2008 when South Korea was ruled by liberal presidents who shipped large quantities of aid to Pyongyang as they sought to improve ties. The last of those projects, a North Korean factory complex run with North Korean workers and South Korean managers and capital, shut down this spring.

North Korea also wanted Seoul to restart an era of rapprochement by commemorating past joint statements on reunification and joint economic cooperation efforts. But Seoul balked at this; it has demanded apologies for past bloodshed before allowing such exchanges.

North Korea’s interest in talks followed its longstanding cycle of alternating between provocative behavior and attempts to seek dialogue in what analysts say are efforts to win outside concessions.

After U.N. sanctions were strengthened following North Korea’s third nuclear test in February, the country, which is estimated to have a handful of crude nuclear devices, threatened nuclear war and missile strikes against Seoul and Washington. North Korea has also conducted recent nuclear tests and long-range rocket launches.

Some observers believe Pyongyang was trying to ease ties with Seoul, Tokyo and Beijing as a way to win coveted talks with Washington, which it believes could grant it aid and security guarantees.

South Korean President Park Geun-hye has made trust-building with Pyongyang a hallmark of her nascent rule, even as she vows strong counterstrikes to any North Korean attacks.

There was skepticism in Seoul about the talks even before they collapsed.

“We cannot be overly hopeful about inter-Korean relations, which reached a new low not long ago,” the conservative Korea JoongAng Daily said in an editorial Tuesday. “We have experienced numerous setbacks during past talks with Pyongyang.”